Pumping unit

ABSTRACT

A pumping unit comprising at least two piston pumps, a first or &#39;&#39;&#39;&#39;preceding&#39;&#39;&#39;&#39; pump and a second or &#39;&#39;&#39;&#39;succeeding&#39;&#39;&#39;&#39; pump. The chambers of the pump cylinders are connected with pneumatic or hydraulic accumulators having an adjustable initial pressure. The unit comprises several shut-off devices, viz., a first shut-off device connecting the accumulators of each pump with the atmosphere; a second shut-off device interconnecting the accumulators; a third shut-off device connecting the discharge manifold of the first pump with the suction manifold of the second pump; and a one-way check valve connecting the suction manifold of the first pump with that of the second pump. Another check valve interconnects the discharge manifolds of the pumps.

United States Patent [1 1 Roschupkin et a1.

1 Oct. 1,1974

I PUMPING UNIT 22 Filed: May 29,1973

21 Appl. No.1 364,413

[52] US. Cl. 417/62, 417/276 [51] Int. 1C1. F04b 23/04, F04b 49/00 [58]Field of Search 417/62, 274-277,

[56] References Cited UNITED STATES PATENTS 6/1930 Riesner 417/44010/1940 Vickers 2/1949 Meitzler 417/274 Primary Examiner-William L.Freeh Assistant ExaminerG. P. LaPoin'te Attorney, Agent, or Firm-Waters,Roditi, Schwartz & Nissen [5 7] ABSTRACT A pumping unit comprising atleast two piston pumps, a first or preceding pump and a second orsucceeding pump. The chambers of the pump cylinders are connected withpneumatic or hydraulic accumulators having an adjustable initialpressure. The unit comprises several shut-off devices, viz., a firstshut-off device connecting the accumulators of each pump with theatmosphere; a second shut-off device interconnecting the accumulators; athird shut-off device connecting the discharge manifold of the firstpump with the suction manifold of the second pump; and a one-way checkvalve connecting the suction manifold of the first pump with that of thesecond pump. Another check valve interconnects the discharge manifoldsof the pumps.

7 Claims, 5 Drawing Figures SHEET 2 [IF 5 PATENT {U GET 11974 mirl F maxPATENTE'U H974 308138.841

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sum u or s PATENI EU BET 4 SHEET 5 OF 5 PUMPING UNIT The presentinvention relates to the pump-building industry and more specifically itrelates to pumping units. The invention can be utilized mostsuccessfully for handling abrasive-containing liquids in drilling deepwells.

Known in the art is a pumping unit for drilling deep wells (see, forexample, A. A. llsky Calculations and designing of drilling equipment,"USSR, 1957). The known pumping unit comprises two piston pumps. Eachpump has two working cylinders with pistons which divide the inner spaceof the cylinders into two chambers. These chambers are in communicationwith the suction and discharge manifolds for the working fluid. Thedischarge manifolds of the piston pumps are combined into a commondischarge line.

in the majority of cases such pumping units ensure either parallel orseparate operation of the pumps, and their disadvantage lies in that thepower of the pump drive converted into hydraulic power is used withinstrictly definite limits which depend on the maximum pump capacity andmaximum permissible discharge pressure of each separate pump.

The range of power utilization of the pump drive can be widened byconnecting the pumps in tandem which raises their discharge pressures.

Theoretically, tandem operation of piston pumps can be ensured only byproviding them with an adjustable drive with a series characteristic(e.g. Leonard drive or a hydrodynamic transmission drive) since in atandem connection of pumps with an inflexible characteristic the entireload would be carried by the pump whose capacity is even slightly higherthan that of the other pump. It must be noted that an absolute equalityof capacities of any two piston pumps is practically unattainable.

However, an inherent disadvantage of adjustable drives lies in that theyreduce considerably the effective power of the pumping unit whereasheavy rotating masses and rather inflexible mechanical characteristicsof the drive hinder uniform distribution of the pressure differencebetween the tandem pumps which, in turn, cuts down the service life ofthe wearing replaceable parts of the pump.

Another disadvantage lies in that the use of these types of adjustabledrives fails to eliminate the irregularity of piston motion in theworking cylinders of the pump, said irregularity being caused by thekinematics of the crank gear. Therefore, owing to considerable pressurefluctuations at the discharge side, piston pumps with this adjustabledrive cannot render a reliable service for producing superhigh pressuresduring tandem operation.

An object of the present invention resides in providing a pumping unitwhich widens the power utilization limits of the pump drive and iscapable of producing superhigh discharge pressures.

Another object of the invention resides in improving the reliability andextending the life of pump wearing parts during operation at superhighdischarge pressures.

Still another object of the invention is to produce a uniformnonpulsating flow of fluid during operation at superhigh dischargepressures.

And, finally, a further object is to distribute uniformly thetransmitted power and the pressure difference between two or moretandem-operating pumps.

In accordance with these and other objects a pumping unit is provided.comprising at least two piston pumps, namely a first and a second pump,each consisting of working cylinders with a piston which divides theirinner spaces into two chambers communicating hydraulically with theworking-fluid suction and discharge manifolds. The discharge manifoldsof the pumps are combined into a common discharge line wherein,according to the invention. at least one chamber of each workingcylinder communicates with at least one pneumatic or hydraulicaccumulator with and adjustable initial pressure, the accumulators ofeach pump being interconnected by a pipeline which communicates with theatmosphere through is first shut-off device while the accumulators ofboth pumps are interconnected by pipelines through a similar shut offdevice.

The discharge manifold of the pump being connected with the suctionmanifold of the succeeding pump by a pipeline through a third shut-offdevice which is operated by a pressure difference between theaccumulators; besides, the suction manifold of the first pump isconnected with the suction manifold of the second pump through a devicepreferably in the form of a pressure-responsive or a one-way valvewhereas their discharge manifolds are interconnected through another,preferably similar device.

Owing to the use in the pumping unit according to the invention ofaccumulators connected to the chambers of the pump working cylinders,the delivery of fluid by each pump is uniform and nonpulsating, whichimproves considerably the reliability and serviceability of the unit atsuperhigh discharge pressures and allows the use of most economicalnon-adjustable electric motors or internal-combustion engines withoutthe usual hydrodynamic transmissions which are used at present and whichconsiderably reduce the effective power of the unit.

The use of shut-off devices in the pumping unit ensures the possibilityof selective parallel and tandem operation of the pumps and. as aconsequence, widens the range of utilization of the pump drive power andpermits building up superhigh discharge pressures.

It is recommended that the first shut-off device be made in the form ofa valve.

it is also advisable that the third shut-off device be made in the formof a cylinder with a piston which divides the inner space of thecylinder into two chambers one of which, accommodating a rod,communicates by a pipe with the hydraulic accumulators of the secondpump while the other chamber is in communication with the accumulatorsof the first pump; the free end of the rod is provided with a cone andthe body of the shut-off device has a seat. When the cone closes theseat, the working fluid does not flow from the discharge manifold of thefirst pump into the suction manifold of the second pump.

In a pumping unit consisting of single-acting piston pumps it isrecommended that the working cylinder of each pump be divided by thepiston into two chambers of which the working one is filled with beingworking fluid while the other, the auxiliary one, is filled with anauxiliary fluid possessing lubricating properties and being free ofmechanical impurities. The auxiliary chambers of each piston pump arethen connected with each other and with the accumulators by a pipeline,

communicating with hydraulic system of the entire unit with make-uppumps. Piston rods in the working chambers are preferably provided withstops, the pistons being free to slide longitudinally along the rods upto these stops. The auxiliary chambers of the second pump cylinders canbe connected with the rod chamber of the cylinder of the third shut-offdevice; the similar chambers of the first pump can be connected with theother chamber of the same cylinder of the third device; in addition, theauxiliary chambers of the working cylinders of the pumps can beinterconnected by a pipe through a valve.

Such pumping units are more convenient in servicing since they have aminimum number of replaceable parts and are more reliable in operationowing to the use of the auxiliary fluid which is characterized bylubricity and is free of mechanical impurities.

It is advisable that the rod of the second pump be made of two sealingelements separated by a shoulder of a gland body from an intermediatechamber filled with the auxiliary fluid and communicating with theaxuiliary chamber of the working cylinder of the first pump.

Such a seal reduces the difference of pressures applied to individualsealing elements, thereby increasing their durability.

It is most recommended that the auxiliary chambers of the workingcylinders of both pumps and the supply source of the hydraulic system beconnected to a device for maintaining uniform distribution of thepressure difference between the pumps when operating in tandem.

It is also recommended that the device for maintaining uniform pressuredistribution be made in the form of a slide valve with three chambers;one of these, with a rod, being connected by a pipeline with theauxiliary chambers of the second pump and with the rod chamber of thecylinder of the third shut-off device, a second chamber of the slidevalve, without a rod, being connected by a pipeline with the auxiliarychambers of the first pump with the rodless chamber of the cylinder ofthe third shut-off device.

A middle chamber of the slide valve is then connected by a pipeline withthe auxiliary chambers of both pumps and with a hydraulic makeup pump. Amovable contact can be provided at one side of the slide valve, e.g. onthe rod, and a fixed contact secured a slide valve body, so that theclosing of these contacts starts an electric drive motor of the make-uppump.

The following description of the present invention is given withreference to the accompanying drawings, in which: a

FIG. 1 is a schematic diagram of an exemplary pumping unit according tothe invention with two doubleacting piston pumps;

FIG. 2 is a diagram showing the power utilization zones of the pumpingunit drive according to the inventron;

FIG. 3 is a schematic showing of the pumping unit according to theinvention with two single-acting controllable pumps;

FIG. 4 is an enlarged longitudinal section of a rod seal of asupcrhigh-pressure pump according to the invention;

FIG. 5 is a schematic illustration, similar to that of HG. 3, of thepumping unit according to the invention with a device for uniformdistribution of the pressure difference between the two pumps.

The pumping unit according to FIG. 1 consists of two piston pumps: apreceding or first pump 1 and a succeeding or second pump 2. Each pumpaccommodates piston 3 sliding in working cylinders 4 and connected torods 5 with a driving crank gear(not shown in the drawing).

The pistons 3 divide the inner space of the cylinders 4 into two workingchambers 6 and 7, each provided with a suction valve 8 and a dischargevalve 9.

Besides, each working chamber 6 and 7 of the pumps 1 and 2 is connectedto a pneumatic or hydraulic accumulator with an adjustable initialpressure, made in the form of a reservoir 10 filled with a compressiblemedium and accommodating a floating piston 11 which separates the mediumfrom the handled fluid. The reservoirs 10 of each pump areinterconnected by a pipeline 12 into a single reservoir common for allthe cylinders 4, and they are connected by a pipe 13 with a source 14 ofpressure of the medium (e.g. a compressor). The medium can be dischargedthrough a valve 15 connected to the pipeline 12. The fluid is admittedinto the chambers 6 and 7 of each pump through a suction manifold 16 anddischarged through a discharge manifold 17.

A damper l8 installed at the discharge side of each pump eliminatespulsation during maximum-capacity operation of the unit. The rods aresealed by a conventional method.

Non-return valves 19 and 20 are installed, respectively, at the inlet'ofthe suction manifold 16 of the pump 2 and at the outlet of the dischargemanifold 17 of the pump 1. The discharge manifolds 17 are combined intoa common discharge line 21. Both valves open towards the discharge line21 when pressure in both discharge manifolds 17 is higher than that inthe discharge line 21. The discharge manifold 17 of the pump 1 isconnected with the suction manifold 16 of the pump 2 by a pipeline 22through a shut-off device 23 operated by the pressure difference betweenthe ac cumulators 10 of the first and the second pumps 1 and 2.

A rod 24 of the shut-off device 23, connected with a piston 25 of acylinder 26, has a cone 24 at the end, said cone being pressed by aspring 27 against a seat 28 of the shut-off device 23. A rod chamber 29of the cylinder 26 is connected by a pipeline 30 with the pipeline 12which interconnects the reservoirs 10 of the pump 2 with the pressuresource 14 and with the outlet valve 15 of the same pump, communicatingwith the atmosphere.

A chamber 31 of the cylinder 26 is connected by a pipeline 32,respectively, with the pipeline 12, the source 14 and the valve 15 ofthe pump 1.

A valve 33 is provided for connecting or disconnecting the pipelines 30and 32.

The diagram in FIG. 2 shows the power utilization ranges of the pumpingunit drives. The diagram illustrates Q P curves i.e., pump capacity Q vspressure P of the working fluid. Points Q,,,,,,, Q,,,,-,,, P andP,,,,-,, denote, respectively, maximum and minimum pump capacities, andmaximum and minimum pump pressures.

The straight line 1 2 gives the characteristic of the pump at maximumcapacity. The straight line 3 is the pump characteristic at a maximumpressure. The curve 2 3 shows the constant power of the pump.

The straight line 5 6 gives the characteristic of the pumping unit atmaximum capacity with parallel operation of the two pumps. Thestraightline l0 8 is the characteristic of the pumping unit at maximumpres sure with tandem-operated pumps.

The line 6 7 is the constant power curve at parallel operation of thetwo pumps while the line 78 is a similar curve characterizing the tandemoperation of the two pumps.

During operation of one pump the power utilization zone is limited bypoints 0, 1, 2, 3, 4, 0. During parallel operation of two pumps the zoneis limited by points 0, 5, 6, 7, 4, 0. During parallel and tandemoperation of the pumps in the unit according to the invention, the zoneis limited by points 0, 5, 6, 8, 9, 0.

As can be seen from the chart in FIG. 2 the power utilization zone ofthe pumping unit is largest when parallel operation of the pumps iscombined with tandem operation and this is used in the presentinvention.

The pumping unit shown in FIG. 3 comprises two single-acting pistonpumps 1 and 2. Each pump has working cylinders 34 divided by a piston 35into two chambers. One of these, a working chamber 36, is filled withthe working fluid while another an auxiliary chamber 37 containsauxiliary fluid. The auxiliary fluid possesses lubricating propertiesand is free of mechanical impurities. The working chambers 36 of thecylinders 34 accommodate stops 38 secured to rods 39 of the pistons 35.The pistons 35 are free to slide longitudinally along the rods 39 to thestops 38.

The rods are provided with seals 40. Like the pumps illustrated in FIG.I the pumps shown in FIG. 3 have a suction manifold 16, a suction valve8, a discharge valve 9, a discharge manifold 17; a damper 18 forsuppressing pulsations, a non-return valve 19 installed at the inlet ofthe suction manifold 16 of the second pump 2; a non-return valve 20installed at the outlet from the discharge manifold 17 of the pump 1; adischarge line 21; a pipeline 22 connecting the discharge manifold 17 ofthe pump 1 with the suction manifold 16 of the pump 2 through theshut-off device 23 which comprises a rod 24 with a cone 24', said rodbeing connected with the piston 25 of the cylinder 26 and pressed by aspring 27 against the seat 28 of the shut-off device 23.

The chamber 29 with the rod 24 of the cylinder 26 is connected by apipeline 30 with the auxiliary chambers 37 of the pump 2 while the otherchamber 31 of the cylinder 26 is connected by a pipeline 32 with theauxiliary chambers 37 of the pump 1.

The auxiliary chambers 37 of each pump are connected with each other bya pipeline 4] and with an accumulator made in the form of anadjustable-volume reservoir 42 filled with the compressible medium andprovided with a diaphragm 43 which separates the medium from theauxiliary fluid.

A pipeline 44 communicates the auxiliary chambers 37 of the cylinders 34with a make-up pump 45 of a hydraulic system, including a check valve 46and a reservoir 47 for the auxiliary fluid. The chambers 37 of the pumps1 and 2 are in communication through the pipelines 30 and 32 and througha check valve 48.

The seal 40 of the rod 39 of the succeeding pump 2 has an intermediatechamber 49 (FIG. 4) which is filled with the auxiliary fluid from thereservoir 42 (FIG. 3) of the first pump I through a channel 50 drilledin the body of the hydraulic cylinder 34 of the pump 2 and through achannel SI drilled in the body of a gland 52.

The chamber 49 (FIG. 4) is a cylindrical recess in a separatingshoulder53 of the body of the gland 52. Located right and left of theseparating shoulder 53 are elastic sealing elements 54 with underlyingplastic rings 55 pressed against the separating shoulder 53 by a nut 56at the side of the working cylinder 34 and a bushing 57 at the driveside. The fixed joint between the body of the gland 52 and the workingcylinder 34 is sealed by cups 58 to prevent fluid leaks.

Inasmuch as in the tandem-operated pumping unit (FIG. 3) the pressure ofthe medium in the reservoir 42 of the second pump 2 is twice thepressure in the first pump ll, each sealing element 54 (FIG. 4) issubjected only to half the total pressure built up in the pumping unit.

Shown in FIG. 5 is a schematic illustration of such a pumping unit witha device for maintaining uniform distribution of the pressure differencebetween the pumps 1 and 2.

The uniform distribution of pressure difference between the pumps 1 and2 of the unit is ensured by a slide valve 59 which has three chambers60, 61, 62. The chamber 60 with a rod communicates through the pipeline30 with the reservoir 42 of the pump 2 and with the chamber 29 of theshut-off device 23. The chamber 61 communicates through the pipeline 32with the reservoir 42 of the pump 1 and with the space 31 of the device23.

The chamber 62 of the slide valve 59 located be- I tween bands 63 of theslide valve 59 communicates with the pipelines 30 and 32, with thereservoirs 42 of the pumps 1 and 2 and, by a pipeline 64, with the makeup pump 45 of the hydraulic system. At one side, the slide valve 59 isprovided with the rod 65 whose crosssectional area is twice smaller thanthat of the band 63 of the same slide valve 59. A movable contact 66 ofthe rod 65 can close a fixed contact 67 of a power supply 74 for themake-up pump 45. The fixed contact 67 is secured on the body of theslide valve 59. Besides, the rod 65 is connected with a handle 68 by ajoint 69.

At the inlets of the spaces 60, 61 of the slide valve 59 are installed,respectively, throttles 70 and 71 for damping self-excited vibrations ofthe slide valve.

Adjustable safety valves 72 of the pumps 1 and 2 are intended to limitpressure in the reservoirs 42 of the pumps 1 and 2. A button 73 servesfor starting the pump 45 during manual control of the pumping unit.

The pumping unit incorporates the source 74 of electric power for themake-up pump 45 and a reservoir 75 with auxiliary fluid.

The handle 68 is mounted on an axle 76, has a retainer 77 for stoppingthe slide valve in the middle position as shown in FIG. 5, and isinstalled on a bracket 78 connected with the body of the slide valve 59.The slide valve 59 is loaded by a spring 79.

The pumping unit shown in FIG. 1 functions as follows: the working fluidenters the suction manifolds 16 of the pumps 1 and 2, passes through theworking cylinders 4 and is forced out by the pistons 3 into the discharge manifolds 17 of the pumps 1 and 2.

The capacity of the pumping unit depends on the pressure of thecompressible medium in the reservoirs 10 of the pumps 1 and 2.

If the pressure of the medium in the reservoirs 10 of the pumps 1 and 2is the same and is higher than the 1 pressure of the working fluid inthe discharge line 21,

the pistons 11 in the reservoirs 10 are in the initial positions, bothpumps 1 and 2 work in parallel, i.e., their capacity is equal to thetotal capacity of the two pumps. in this case the shut-off device 23 isclosed, because the cone 24 of the rod 24 is pressed against the seat 28by the surplus force acting on the piston 25 in the direction of theseat 28 at equal pressures of the medium in the chambers 29 and 31 ofthe cylinder 26. Both nonreturn valves 19 and 20 are open. The valve 19admits fluid into the suction manifold 16 of the pump 2 while the valve20 admits fluid delivered by the pump 1 into the discharge line 21.

The pumps 1 and 2 delivering fluid into the common discharge line 21 canoperate in parallel, both at a maximum capacity and at a partialcontrollable capacity of the pumps 1 and 2. g

The process of controlling the capacity of each of the two pumps in thepumping unit consists in the followmg.

During each discharge stroke, for example in chamber 6, part of thefluid is forced out through the discharge valve 9 while another partenters the reservoir 10 and moves the piston 11.

Then, during the suction stroke, the working fluid that has entered thereservoir 10 is again forced out by the pressure of the medium into thechamber 6 and, only after the piston 11 returns to the initial position,will the suction valve 8 open. The lower the pressure of the mediumcreated by its source, the larger the displacement of the piston 11 and,correspondingly, the lower the pump capacity.

The capacity of the pumping unit can be controlled at will at a constanthydraulic resistance of the well where the unit is used, by changing thepressure of the medium in the reservoirs 10 of the pumps 1 and 2.

The capacity of the pumping unit can also change automatically andinstantaneously as a result of changes in the hydraulic resistance ofthe well in which case an increase in the hydraulic resistance willcause automatic reduction of the unit capacity and vice versa.

During parallel operation with the pumps discharging fluid into a singlepipeline, the hydraulic power will be evenly distributed between the twopumps 1 and 2 if the valve 33 interconnects the reservoirs 10 of thepumps 1 and 2 so that the pressures in said reservoirs are the same.

Owing to a flexible O p characteristic of the pumps, which means thattheir capacity changes automatically with the load (hydraulicresistance) as in centrifugal pumps, the pumps can also be used fortandem operation.

Therefore, if the pressure built up by the unit fails to satisfy thewell drilling requirements, the pumps can be switched over to tandemoperation For this purpose the reservoirs 10 of the pumps 1 and 2 mustbe disconnected by the valve 33.

It is most expedient to set a pressure of the medium in the reservoirs10 of the first pump 1 at half the desired pressure in the dischargeline 21 of the pumping unit.

Using a compressor 14, pressure of the medium in the reservoirs 10 ofthe second pump 2 is bulit up to the value of the total pressure in thedischarge line 21. Then. owing to a pressure rise in the chamber 29communicating with the reservoirs l0 of the pump 2, the piston 25 willovercome both the resilient force of the spring 27 and the pressure inthe space 31, and will move all the way to the right, as shown in thedrawings, the rod 24 admitting the fluid from the discharge manifold 170f the pump 1 into the suction manifold 16 of the pump 2.

Owing to the rise of pressure, the non-return valves 19 and 20 willclose automatically and the pumps 1 and 2 of the pumping unit will beswitched over to tandem operation.

During tandem operation of the pumps 1 and 2 the unit capacity can alsobe controlled by changing the pressure of the medium in the reservoirs10 of the pumps in a proportion of 1:2 which will ensure uniformdistribution of the input power between the two pumps. On changes in thehydraulic resistance of the well the flexible Q-P curve of the pumps 1and 2 will cause automatic changes in the capacity of the pumping unit.

Control of the pumping unit according to FIG. 1, carried out by anoperator, consists in selecting and maintaining the required relation ofpressures of the medium in the reservoirs 10 of the pumps 1 and 2.

The pumping unit according to FIG. 1 features the following advantagesover drilling pumping units in current use:

1. Owing to the fact that the pressure of the working fluid at the inletof the second pump 2 is half the pressure built up by the unit, theworking load is distributed evenly between the two pumps 1 and 2 and thepressure difference applied to the parts of each pump (pistons 3 andvalves 8, 9) is equal to half the maximum pressure; this extendsconsiderably their service life at superhigh pressures of the dischargedfluid in the well and while handling abrasive fluids.

2. Owing to the fact that both pumps 1 and 2 have reservoirs 10 filledwith the medium and communicating with the chambers 6 and 7 of the pump1 or 2, the delivery of the working fluid by each pump is uniform andnonpulsating which promotes considerably the reliability and efficiencyof the pumping unit during tandem operation at superhigh dischargepressures.

3. The employment of the pumping unit according to the invention widensconsiderably the range of power utilization of drilling pump drives,which can be seen on the chart in FIG. 2 where the power utilizationzone of the drive is as follows:

for one operating pump a zone limited by points 0, l, 2, 3, 4, 0;

for parallel operation of two pumps a zone limited by points, 0, 5, 6,7, 4, 0;

for parallel and tandem operation of pumps in the unit according to theinvention, a zone limited by points 0, 5, 6, 8, 9, 0.

4. Owing to the use of the reservoirs l0 filled with the medium andcommunicating with the chambers 6 and 7 of the pumps 1 and 2, thepumping unit can be driven by the most economical non-adjustableelectric motors or internal combustion engines without hydrodynamictransmissions, whose present employment reduces considerably theeffective power of the unit drive.

Like the pumping unit described herein before, the pumping unitaccording to FIG. 3 is capable of functioning both with a parallel and atandem connection of the pumps 1, 2.

During parallel operation the pressure of the medium in the reservoirs42 of the pumps 1 and 2 is maintained equal because the auxiliarychambers 37 of the pumps 1 and 2 are in communication through the checkvalve 48.

During tandem operation of the pumps, the valve 48 disconnects theauxiliary chambers 37 and the reservoirs 42 of the pumps 1 and 2.

The volume of the auxiliary fluid filling the auxiliary chamber 37 andthe reservoir 42 of the second pump 2 is increased by the make-up pump45 which compresses the medium in the reservoir 42 and increasespressure. This raises the pressure in the chamber 29 of the cylinder 26of the shut-off device 23 so that the pis ton 25 shifts the rod 24 allthe way to the right, putting the discharge manifold 17 of the pump 1 incommunication with the manifold 16 of the pump 2 through the pipeline22. The valves 19 and 20 close automatically.

The capacity of the pumps during both parallel and tandem operation canbe controlled by changing the volume of the auxiliary fluid in thereservoirs 42 of the pumps 1 and 2 and, as a consequence, by changingthe pressure of the medium in said reservoirs 42.

Inasmuch as the piston 35 is free to move longitudinally along the rod39 to the stops 38, it will cover only a part of its complete travel inthe cylinder 34, coming short of the stops 38. The travel of the piston35 will be smaller proportionally to the valve by which the dischargepressure exceeds the initial pressure of the medium in the reservoirs42.

If the pressure of the medium is higher than the discharge pressure, thepistons 35 will be pressed against the stops 38 and will make a completestroke in the working cylinder 34.

The pumps of this design are more convenient to service because theyhave a minimum number of replaceable parts, and they are more reliablein operation due to the use of the auxiliary fluid which possesseslubricating properties and is free of mechanical impurities. These pumpsare better suited to automation and remote control, which makes itpossible to maintain automatically the uniform distribution of thepressure difference between the two pumps of the unit. However withequal dimensions of the pumps the capacity of this unit is lower thanthat of the unit shown in FIG. 1.

The pumping unit shown in FIG. 5 ensures uniform distribution of thepressure difference in the pumps 1 and 2 during their parallel andtandem operation.

The pumps 1, 2 operate in parallel when the rod of the slide valve 65 isfixed in the middle position by the handle 68 and the retainer 77. Inthis case the reservoirs 42 of the pumps 1 and 2 are in communicationand have the same pressure of the medium.

The required discharge pressure is maintained either by the operator orautomatically by the conventional methods, in this case with the aid ofa contact-pressure gauge (not shown in the drawing).

The pumping unit is switched over to tandem operation as follows:

1. The safety valve 72 of the pump 1 is set to a pressure twice lowerthan the expected pressure in the discharge line 21.

2. The safety valve 72 of the pump 2 is set to a pressure expected inthe discharge line 21.

3. The handle 68 is taken off the retainer 77.

4. The pump 45 sets automatically the preset pressures in the reservoirs42 of the pumps I and 2.

In view of the fact that the pressure of the fluid on both faces of theslide valve is equal at the initial period of time, after taking thehandle 68 off the retainer 77, and that the area of the slide valve inthe chamber 60 is twice smaller than that in the chamber 61, the rod 65of the slide valve 59 moves upward. The band 63 covers the channel 32and the contact 66 closes the contact 67 thus starting the makeup pump45 of the hydraulic system.

When pressure in the reservoirs 42 of the pump 2 becomes twice higherthan that in the reservoirs 42 of the pump 1, the forces acting on thefaces of the slide valve in the spaces 60 and 61 will be equalized andthe slide valve will open the contacts 66 and 67. The springs 79 and thedampers 70 and 71 will stop the slide valve 59 in a position ofequilibrium, and the band 63 will deny access of the fluid from thechannel 30 into the channel 32.

At a drop of pressure in the reservoir 12 of the pump l the slide valve59 will return to the initial position and will keep the pipelines 30and 32 in communication until the relation P 2P is reached where P, isthe pressure in the reservoir 42 of the pump 1 and P is the pressure inthe reservoir 42 of the pump 2.

The pressure in the reservoirs 42 of the pumps 1 and 2 can be increasedby starting the :make-up pump 45 of the hydraulic system by means of thebutton 73, if this pressure is lower than that for which the safetyvalves 72 of the pumps 1 and 2 are set. or it can be decreased byadjusting the setting pressure of the safety valve 72 of the pumps 1 and2.

The pumping unit shown in FIG. 5 ensures:

1. Parallel and tandem operation of the pumps.

2. Superhigh discharge pressures at a permissible pressure differenceacting on all replaceable wearing parts.

3. Automatic uniform distribution of the power and the pressuredifference between the two pumps.

4. Uniform flow of the discharged fluid.

The pumping unit according to the present invention will allow:

a. raising the efficiency of drilling by increasing the pressuredifference used in the nozzles of jet bits while drilling wells;

b. reducing considerably the time required for auxiliary operations suchas restoring the circulation of the drilling fluid and equalizing itsparameters.

We claim:

I. A pumping unit comprising at least two piston pumps, namely a firstor preceding pump and a second or succeeding pump; working cylinders insaid pumps; pistons dividing the inner spaces of each of said cylindersinto two chambers; a suction manifold admitting working fluid to saidcylinders and communicating hydraulically with said chambers; dischargemanifolds delivering the working fluid to consuming units and alsocommunicating with said chambers; a common discharge lineinterconnecting said discharge manifolds; a hydraulic system including asupply source for the working fluid and hydraulic accumulators for saidpumps, connected to said chambers, with an adjustable initial pressure,for changing the rate of fluid flow through said pumps in accordancewith the prevailing discharge pressure; a first shut-off device; apipeline interconnecting said accumulators and communicating with theatmosphere through said first shut-off device; a second shut-off deviceinterconnecting said accumulators and being similar to said firstshut-off device; a third shut-off device interconnecting said dischargemanifold of the first pump with said suction manifold of the second pumpand operated by a pressure difference between said accumulators; aone-way check valve interconnecting said suction manifold of the firstpump with that of said second pump; and another check valve, similar tosaid one-way check valve, interconnecting said discharge manifolds.

2. The pumping unit as defined in claim 1, wherein said first shut-offdevice is made in the form of a valve.

3. The pumping unit as defined in claim 1, wherein said third shut-offdevice is made in the form of a cylinder with a piston which divides theinner space of said cylinder into two chambers; one of which, with arod,

is connected by a pipeline with said accumulators of the second pump,while another chamber is connected with said accumulators of the firstpump; the free end of said rod being fitted with a cone, and a body ofsaid third shut-off device being provided with a seat so that in theclosed position, when said cone closes said seat, the working fluid isprevented from flowing from said discharge manifold of the first pumpinto said suction manifold of the second pump.

4. The pumping unit as defined in claim 1, further comprisingsingle-acting piston pumps with working cylinders, each divided bypistons into two chambers; one of which, a working chamber, is filledwith the working fluid while the other, an auxiliary chamber, containsan auxiliary fluid with lubricating properties and free of mechanicalimpurities; said auxiliary chambers of the pumps communicating with eachother and with said accumulators through a pipeline and being connectedto said hydraulic system with make-up pumps; wherein rods of saidworking chambers have stops and said pistons are free to slidelongitudinally along said rods up to said stops; said auxiliary chambersof the second pump are in communication with said rod-containing chamberof the cylinder of said third shut-off device, and similar chambers ofsaid first pump are in communication with said other chamber of the samecylinderof said third shut-off device; and wherein said auxiliarychambers of the working cylinders are interconnected by a pipelinethrough a valve.

5. The pumping unit as defined in claim 4, wherein said second pump isprovided with a seal for said rod. said seal consisting of two sealingelements separated by a shoulder of a gland body, and an intermediatechamber which is filled with the auxiliary fluid and communicates withsaid auxiliary chamber of the working cylinder of the first pump.

6. The pumping unit as defined in claim 4, wherein said auxiliarychambers of the working cylinders and said supply source are connectedto a device for ensuring uniform distribution of the pressure differencebetween said pumps during tandem operation.

7. The pumping unit as defined in claim 6, wherein said device ensuringuniform pressure distribution is made in the form of a slide valve withthree chambers; one of which, with a rod, communicates through apipeline with said auxiliary chambers of the second pump and with saidrod chamber of the cylinder of said third shut-off device; anotherchamber of said slide valve, which is without a rod, communicatesthrough a pipeline with said auxiliary chambers of the first pump andwith said rodless chamber of said cylinder of the third shut-off device,while a middle chamber of said slide valve communicates through apipeline with said auxiliary chambers of both pumps and with a make-uppump of said hydraulic system; said rod at one side of said slide valvebeing provided with a movable contact while a body of said slide valvehas a fixed contact which interacts with said movable contact to switchon said make-up pump.

1. A pumping unit comprising at least two piston pumps, namely a firstor preceding pump and a second or succeeding pump; working cylinders insaid pumps; pistons dividing the inner spaces of each of said cylindersinto two chambers; a suction manifold admitting working fluid to saidcylinders and communicating hydraulically with said chambers; dischargemanifolds delivering the working fluid to consuming units and alsocommunicating with said chambers; a common discharge lineinterconnecting said discharge manifolds; a hydraulic system including asupply source for the working fluid and hydraulic accumulators for saidpumps, connected to said chambers, with an adjustable initial pressure,for changing the rate of fluid flow through said pumps in accordancewith the prevailing discharge pressure; a first shutoff device; apipeline interconnecting said accumulators and communicating with theatmosphere through said first shut-off device; a second shut-off deviceinterconnecting said accumulators and being similar to said firstshut-off device; a third shut-off device interconnecting said dischargemanifold of the first pump with said suction manifold of the second pumpand operated by a pressure difference between said accumulators; aone-way check valve interconnecting said suction manifold of the firstpump with that of said second pump; and another check valve, similar tosaid one-way check valve, interconnecting said discharge manifolds. 2.The pumping unit as defined in claim 1, wherein said first shut-offdevice is made in the form of a valve.
 3. The pumping unit as defined inclaim 1, wherein said third shut-off device is made in the form of acylinder with a piston which divides the inner space of said cylinderinto two chambers; one of which, with a rod, is connected by a pipelinewith said accumulators of the second pump, while another chamber isconnected with said accumulators of the first pump; the free end of saidrod being fitted with a cone, and a body of said third shut-off deVicebeing provided with a seat so that in the closed position, when saidcone closes said seat, the working fluid is prevented from flowing fromsaid discharge manifold of the first pump into said suction manifold ofthe second pump.
 4. The pumping unit as defined in claim 1, furthercomprising single-acting piston pumps with working cylinders, eachdivided by pistons into two chambers; one of which, a working chamber,is filled with the working fluid while the other, an auxiliary chamber,contains an auxiliary fluid with lubricating properties and free ofmechanical impurities; said auxiliary chambers of the pumpscommunicating with each other and with said accumulators through apipeline and being connected to said hydraulic system with make-uppumps; wherein rods of said working chambers have stops and said pistonsare free to slide longitudinally along said rods up to said stops; saidauxiliary chambers of the second pump are in communication with saidrod-containing chamber of the cylinder of said third shut-off device,and similar chambers of said first pump are in communication with saidother chamber of the same cylinder of said third shut-off device; andwherein said auxiliary chambers of the working cylinders areinterconnected by a pipeline through a valve.
 5. The pumping unit asdefined in claim 4, wherein said second pump is provided with a seal forsaid rod, said seal consisting of two sealing elements separated by ashoulder of a gland body, and an intermediate chamber which is filledwith the auxiliary fluid and communicates with said auxiliary chamber ofthe working cylinder of the first pump.
 6. The pumping unit as definedin claim 4, wherein said auxiliary chambers of the working cylinders andsaid supply source are connected to a device for ensuring uniformdistribution of the pressure difference between said pumps during tandemoperation.
 7. The pumping unit as defined in claim 6, wherein saiddevice ensuring uniform pressure distribution is made in the form of aslide valve with three chambers; one of which, with a rod, communicatesthrough a pipeline with said auxiliary chambers of the second pump andwith said rod chamber of the cylinder of said third shut-off device;another chamber of said slide valve, which is without a rod,communicates through a pipeline with said auxiliary chambers of thefirst pump and with said rodless chamber of said cylinder of the thirdshut-off device, while a middle chamber of said slide valve communicatesthrough a pipeline with said auxiliary chambers of both pumps and with amake-up pump of said hydraulic system; said rod at one side of saidslide valve being provided with a movable contact while a body of saidslide valve has a fixed contact which interacts with said movablecontact to switch on said make-up pump.